The three power-supplying phase feeders (conductors) are monitored to detect electrical fault conditions on the distribution lines of an electrical power distribution network (grid). To clear or repair the faults, such as short circuits, it is important to first determine the fault location. In conventional overhead distribution systems there is a normal power flow direction, with power flow in the opposite direction (reverse power flow) only for contingency purposes. Reverse direction power flow is always known by the system operations staff and accounted for in systems operation and maintenance.
However, the fault location task is complicated in networked power distribution systems, such as urban and underground power distribution networks, because the direction of power flow through a particular line can change over time in response to load and source changes. Since power flow direction at any time is not known, it is problematic to use conventional non-directional fault indicators to determine fault location.
Other problems are encountered in detecting and locating faults in an underground network. Back fed current complicates fault detection and location. Network protector operation may be inconsistent and some protectors may not close after a fault has been repaired. This failed operation may leave segments of the network unenergized and unreported. The relatively short distance and attendant interference between conductors in the underground network also complicates fault detection.
Accordingly, an improved directional fault indicator apparatus for detecting a direction to a fault in an electrical power distribution network in the presence of typical power fluctuations and power flow direction changes is desired.
To shorten the time required to restore power on an underground network, the network includes splice points at known locations. Each splice point is an access point in a submersed or underground vault with about 1 to 11 three-phase primary feeders supplying power to the network at the splice point. Each splice point may also have access to a 120 VAC source that is independent of the electricity on the power-supplying phase conductors.
In accordance with common practice, the various described features are not drawn to scale, but are drawn to emphasize specific features relevant to the invention. Reference characters denote like elements throughout the figures and text.